Cryogenian-to-Cambrian 24-isopropylcholestanes are measured compounds, but sampled Rhizaria can synthesize their sterol precursors, so these rocks do not uniquely establish Demospongiae.
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References / paperPutative sponge biomarkers in unicellular Rhizaria question an early rise of animals
Nettersheim, B.J.; Brocks, J.J.; Schwelm, A.; Hope, J.M.; Not, F.; Lomas, M.; Schmidt, C.; Schiebel, R.; Nowack, E.C.M.; De Deckker, P.; et al.
Year2019
Source roleprimary-study
DOI / ID10.1038/s41559-019-0806-5
Fitness and scope
taxonomy · methods
Demonstrates biosynthesis of candidate sterol precursors in sampled Rhizaria, directly limiting taxonomic specificity of the biomarker inference.
Claim ledger
Cryogenian sterane records used on the Demospongiae route are a contested geochemical attribution to sponge-grade sources; they do not establish a demosponge crown origin, body fossil or global first appearance.
claim:taxon:demospongiaeDemospongiae is displayed at 635–0 Ma only as a contested biomarker-to-living navigation anthology: Cryogenian 24-isopropylcholestanes are not taxonomically exclusive to demosponges and do not establish a body-fossil FAD, crown origin or continuous global occupancy.
claim:taxon:demospongiae:range-boundary-rc50